Single unit air-water heating appliance

ABSTRACT

A single unit heating appliance comprising an air plenum and a water heating container with a heat exchanger extending into the plenum is shown. Water is heated by a burner and some of its heat is transferred to the heat exchanger which transfers the heat to ambient air passing thereover.

United States Patent 1191 Marshall Sept. 3, 1974 [54] SINGLE UNITAIR-WATER HEATING 2,533,692 12/1950 Rice 126/101 APPLIANCE 2,998,0038/1961 Grooms, Jr.- 126/101 3,033,192 5/1962 Bogren 237/19 Inventor: J Ma 3 Rose Seal 3,404,674 10/1968 Albert 126/101 Beach, Calif. 907403,469,075 9/1969 Barbier 126/101 [22] Filed: Oct. 12, 1972 PrimaryExaminer-William E. Wayner 1 1 pp 296,912 Assistant Examiner-William E.Tapolcai, Jr.

Attorney, Agent, or Firm-Philip Hoffman [52] US. Cl 236/9 R, 126/101,237/19 [51] Int. Cl. F24h 6/00 [57] ABSTRACT [58] Field of Search237/19; 126/101; A single unit heating appliance comprising an airplenum and a water heating container with a heat exchanger extendinginto the plenum is shown. Water is [56] References cued heated by aburner and some of its heat is transferred UNITED STATES PATENTS to theheat exchanger which transfers the heat to aml,56l,898 11/1925 Antisell165/179 bient air passing thereover.

2,526,464 10/1950 Folk 126/101 2,529,977 11 1950 Thomas 237 19 4 Clams,4 Drawing Figures Pmmmw awn 3.833.170.

SIEEI 1N2 Fig. 1. I

, Fig. 2.

SINGLE UNIT AIR-WATER HEATING APPLIANCE This invention relates generallyto air and water heaters, and more specifically to single unit air-waterheating appliances which use hot water in conjunction with a heatexchanger to heat ambient air in residential quarters. The single unitair-water heating appliance of this invention is referred to herein andin the claims as a hydro-furnace.

Heating systems for use in residential and mobile homes abound in theart and are varied in form. For example, there are warm air furnaces,forced air furnaces, fuel burning furnaces, space heaters, combinationair and water heaters, to name a few. In the case of simple air heaters,the cold air is usually passed through a fuelbuming furnace and forcedout into ducts which direct the warm air to variousparts of the house.Dust particles in the air are charred as they pass through the furnace,causing air contamination and creating a buildup of soot on the airregisters and ceilings. Space heaters are designed to heat only thespace or room in which they are situated, consequently, a heater isrequired for each room in a house. Combination air and water heatersusually heat cold air by having the air pass over the hot watercontainer or by passing the cold air through or over the hot waterfurnace or both. Independent control of the heating of the air and ofthe water is not available in such systems.

A specific example of the prior art is a patent byK. M. Ronan et al.,entitled Combination Water and Space Heater, U.S. Pat. No. 3,269,382.Therein Ronan shows a potable water container above a fuel burningfurnace with a passage therebetween. The air is heated by first passingover the potable water container and then through the aforementionedpassage. Aside from the fact that this is a space heater and istherefore limited in use, it has the further disadvantage that the waterfurnace controls the heating of the air. When the temperature of thepotable water is at its required value, the furnace turns off and theheat supplied to the air is diminished to the heat available from thesurface of the hot water container as the air passes over it. This isthe case regardless of the temperature of the air in the room beingheated, because the room temperature does not control the water furnace.This is true of all heating systems which heat air by means of the waterfurnace. In a forced air system this could result in cold air filling acold room, thereby providing an undesired effect.

Another specific example of the prior art is described in a patent by J.R. Piper, entitled Heating System, U.S. Pat. No. 3,526,361. Piper usesthe potable hot water as the heat source for heating the air bycirculating the hot water through a series of heat exchange coils, onein each room to be heated and passing the cool air over the heatexchanger. The various heat exchangers are connected in series and thehot water is circulated continuously by a water pump. A thermostat ineach room controls the hot air flow and a thermostat on the watercontainer controls the water furnace.

While Piper provides a flow of clean hot air to each room as well asindependent thermostatic control of the water furnace and the airheating, nevertheless, this system has certain disadvantages. Such aheating system must be installed during the construction of the buildingso that the plumbing can be built into each room. To install this systeminto an existing house, if

possible, would require excessive carpentry because the walls and/orceilings would have to be broken into and subsequently repaired. Thematerials required would be expensive because of the extensive insulatedplumbing needed, the large water pump required to circulate the waterthrough so much plumbing, and the number of heat exchangers, blowers andthermostats employed. Nor can the system be removed easily orinexpensively since it is integrally constructed as part of the house.

A further disadvantage of Pipers system is that no provision is made forair heating during the time a depleted hot water supply is beingreheated. Regardless of its temperature, the water in the water tank isconstantly circulated throughout the system. Thus, when cold water ispresent, such as after someone has taken a long hot shower, the air isbeing blown over cold heat exchangers. The air being forced throughPipers registers is therefore cold at this time and will remain colduntil the water is reheated. The reheating of the water occurs graduallyover a period of perhaps several hours, leaving the residents withoutheat.

There exists today a need for a single self-contained inexpensiveheating appliance which can heat a supply of potable water as well ascold air and control each independently of the other and simultaneouslyavoid contamination of the air. Such a unit would be safer thanconventional furnaces and could be made to furnish all necessary heat toa home in conjunction with ducts of a central heating plan, andparticularly to heat mobile homes where space is scarce. It would bedesirable to have a unit which uses the hot potable water to heat theair and which circulates the water without using a water pump. Thiswould eliminate an expense as well as reduce the number of moving parts.It would also be desirable to have a unit which can supply heated airduring the reheating of a depleted hot water supply within minutes afterdepletion.

Accordingly, it is an object of this invention to provide aself-contained home heating appliance for heating air and potable water.

It is another object of the present invention to provide a combinationair-water heating appliance wherein independent thermostatic controlover the air heating and over the water heating is maintained.

A further object of this invention is to provide a combination air-waterheating appliance wherein the hot water is used to heat the air.

Yet another object of the present invention is to provide a single unitcombination air-water heating appliance which can function without awater pump.

Still another object of this invention is to provide a single unitcombination air-water heating appliance which supplies heated air duringthe reheating ofa depleted hot water supply.

These and other objects and advantages of this invention areaccomplished by a hydro-furnace for heating potable water directly andair indirectly and maintaining continuous independent control over both.The hydro-furnace comprises a housing having a return register, a supplyregister, and a plenum therebetween. Within the housing is disposed awater heating container having a water storage tank, a cold water inlet,a hot water outlet, a flue which extends through the housing, and aheating mechanism, such as a burner, for heating the potable water.Disposed within the plenum is a blower for drawing ambient air throughthe return register and blowing it through the plenum and toward thesupply register. A control mechanism, such as a thermostat, isassociated with both the blower and the heating mechanism and turns themon and off. Associated with the water heater is a heat exchangingmechanism, such as a finned-tube manifold or a set of heat-conductingmembers, which extends from the tank into the plenum and which transfersheat from the hot water to the air in the plenum.

The invention will be described in greater detail in conjunction withthe accompanying drawings in which:

FIG. 1 is a cross-sectional elevational view of the hy-.

dro-furnace according to one embodiment of the invention;

FIG. 2 is a cross-sectional view of the hydro-furnace of FIG. 1 takenthrough section 22;

FIG. 3 is a cross-sectional elevational view of the hydro-furnaceaccording to another embodiment of this invention; and

FIG. 4 is a cross-sectional view of the hydro-furnace of FIG. 3 takenthrough section 44.

Referring now to FIGS. 1 and 2, there is shown an embodiment of thehydro-furnace of this invention comprising a housing 2 having a returnregister 4 disposed in one end 6 thereof and a supply register 8disposed in an opposite end 10 thereof, the space therebetween definingan air plenum 12. A blower 14 is disposed within the housing 2 andadjacent the return register 4 such that it can draw ambient air throughthe return register 4 and blow it through the plenum 12 and toward thesupply register 8. a

A hot water heating container 15 is disposed within the housing 2adjacent the plenum 12 and comprises a water storage tank 16, a fuelburner 18, a finned-tube heat exchanger 20, and a flue 22. The heatexchanger is disposed within the plenum 12 and comprises a manifoldwater pipe 24 having several parallel lateral pipes 26 connected to theupper end 28 of the tank 16 and a return pipe 30 connected to the lowerend 32 of the tank 16. The burner 18 is disposed beneath the tank 16 andaway from the return pipe 30. Several parallel heat-conducting fins 34are attached perpendicularly to the pipes 26, and a hot water outletline 36 for furnishing potable hot water to various hot water faucets isconnected to the return pipe 30. A fuel supply line 38 is provided forsupplying fuel to the burner 18, and a cold water supply line 40 isprovided for furnishing potable water to the tank 16.

A thermostat 42 located within the living quarters to be heated controlsan on-off switch 43 on the blower 14 and is coupled thereto byelectrical wires 44. The blower 14 is turned on and off as the ambienttemperature varies below and above a preselected level, respectively.The burner 18 is thermostatically controlled by another thermostat 46which senses the water temperature at the lower end 32 of the tank 16.Wires 48 couple thermostat 46 to a valve 49 on the burner 18. The watertemperature is maintained within a sufficiently hot range such asbetween 140 and 150 F, for example. Thus, when the temperature of thewater falls below 140 F, the valve 49 is opened and the burner 18 isturned on, and when the temperature reaches 150 F, the valve 49 isclosed and the burner 18 is turned off. The thermostats 42 and 46 workindependently of one another.

The thermostat 46 is placed at the lower end 32 of the tank 16 to ensurethat all the water in the tank 16 is heated to the desired temperature.As the water is heated, it rises to the top in accordance with a wellknown heat transfer principle of physics referred to as convection. Thewater molecules nearest the burner 18 are heated and expand clue to anincreased temperature. These water molecules are lighter than the colderones above, therefore they rise and displace the colder ones whichdescend. If the thermostat 46 were to be placed at the upper end 28 ofthe tank 16, it would sense the desired temperature of 150 F at thatpoint while the temperature at the lower end 32 would be perhaps F orlower. The burner 14 would then shut off before all the water would havebeen heated, thus defeating the purpose of achieving the desiredtemperature throughout the tank 16.

The operation of the hydro-furnace of this invention is best understoodby first considering the steady state condition wherein the water in thetank 16 is between and F. As the ambient air goes below the desired roomtemperature, the blower 14 turns on and blows air across the fins 34 ofthe heat exchanger 20. Heat from the hot water in the pipes 26 istransferred via the fins 34 to the air, which is warmed thereby, and thewater in the heat exchanger 20 is cooled. Ultimately a sufficient amountof cold water will accumulate in the lower end 32 of the tank 16 tolower the temperature at the thermostat 46 below 140 F. At this point,the burner 18 turns on to reheat the water. The heated water rises,enters the heat exchanger 20, is cooled, flows down the return pipe 30,and re-enters the tank 16 where it is reheated. A convection current isthereby established which continuously provides hot water to the heatexchanger 20. This is accomplished notably without the aid of a pump.

- It is preferable to have the convection current established as soon asthe blower 14 is turned on. This can be accomplished with a two-stageburner 18 wherein the thermostat 42, in addition to controlling theswitch 43 on the blower 14, is coupled via wires 45 to a valve 47 whichcontrols the first stage of the burner 18. Thus, when the blower 14 isturned on, the valve 47 is opened and the first stage of the burner 18is turned on simultaneously. The controls could be arranged so thatthermostats 42 and 46 control the first and second stages, respectively,or alternatively, that thermostat 46 controls both stages when theblower 14 is off and only the second stage when the blower 14 is on.Either arrangement is compatible with this invention.

The heat generated by the first stage of the burner 18 should be atleast sufficient to establish the aforementioned convection current. Thesecond stage of the burner 18 should supply sufficient heat to reheatthe water to the desired temperature (for example, 150 F) and would becontrolled by the thermostat 46.

Various other two-stage burners, such as electric or oil burners forexample, may also be satisfactory if otherwise compatible with theteachings herein.

When a hot water faucet is opened, hot water will be drawn from theoutlet line 36, which is connected to the return pipe 30. Thetemperature of the water drawn will be lower than that of the water inthe tank 16 because of the transfer of heat from the water to the airblown across the heat exchanger 20. However, the rate of flow of hotwater through the heat exchanger 20 is increased when the hot waterfaucets are opened,

therefore, the temperature of the water in the return pipe 30 when hotwater is being drawn is significantly higher than when no hot water isdrawn. Thus, a supply of potable hot water at a sufficiently hottemperature is assured so long as there is hot water in the tank 16.

As hot water is drawn, cold water enters the tank 16 to maintain aconstant volume. When sufficient amounts of hot water are drawn, thewater temperature sensed by the thermostat 46 will be low enough to turnon the burner 18, and in the case of a two-stage burner, the secondstage. However, if great amounts of hot water are drawn, as is possibleif two showers are in use simultaneously, for example, the water in thetank 16 may have a temperature only slightly higher than the cold waterentering. The hot water supply is then said to be exhausted and cannotbe replenished while the hot water faucets are open and drawing water.

The time required to reheat the water to the desired temperature of, forexample, 150 F is referred to as the recovery time and is. measured fromthe time the hot water faucets are closed. Heat is supplied by theburner 18 which heats the water in the tank 16. Throughout the recoverytime, heat is available to warm the air blowing past the heat exchanger20 because of the convection current previously discussed. The hot waterrises to the top of the tank 16 and goes into the heat exchanger 20. Ina matter of minutes, the water in the heat exchanger 20 will besufficiently hot to warm the air. For a 30-gallon water heater with aheat capacity of 76,200 BTU and for a blower with an air flow rate of600 cubic feet per minute (cfm), for example, it will take on the orderof 1% hours to reheat all the water in the tank 16 to the desired 150 F.This recovery time will be approximately 95 hour when the blower 14 isoff because then no heat is transferred from the water to the air. Thesetimes are substantially less than the recovery times of 4 hours and 1%hours, respectively, required by Ronan. They are also substantially lessthan the average recovery times for conventional 30-gallon water heaterscurrently on the market.

The burner 18 is set away from the return pipe 30in FIG. 1 and madesmaller in diameter than the tank 16 in FIG. 3 in order to prevent hotwater from travelling up through the return pipe 30. The hot watermolecules tend to rise, as discussed previously. Therefore, by providinglateral space between the burner 18 and the return pipe 30 in this way,the hot water would first have to travel laterally to get to the pipe30. Since the hot water tends to rise, it will do so rather than movelaterally. The circulating convection current is thereby enhanced, andthe heated water will rise and reach the heat exchanger 20 withinseconds. This ensures that the air will be heated even though the hotwater supply is exhausted.

In FIGS. 3 and 4 there is shown another embodiment of the hydro-furnaceof this invention which is distinguishable from the hydro-furnace ofFIGS. 1 and 2 in that the finned-tube heat exchanger 20 is replaced byanother type of heat exchanger 50 comprising multiple lateral heatconducting members 52, such as rods or tubes, extending from within thetank 16 to the plenum 12. This embodiment dispenses with the circulatingconvection current of the first embodiment and, therefore, with thereturn pipe 30 as well. The heat from the hot water in the tank 16 isconducted by the members 52 to the plenum 12 where it is transferred tothe air blown by the blower 14.

The recovery times for the embodiment of FIG. 3 are essentially the sameas for that of FIG. 1. The members 52 experience a temperature gradientcaused by the cool air in the plenum 12 and, therefore, attract heatfrom the hot water rising in the tank 16 and conduct the heat to theplenum 12 where it is promptly transferred to the air. When the members52 are tubes, they may be filled with a liquid under a pressure suchthat the liquid boils at the desired hot water temperature. The liquidwould then be partially vaporized and a steady state would exist in thetube member 52 such that the temperature gradient in the tube member 52would be insignificant. The transfer of heat from the hot water to theair in the plenum 12 would be facilitated thereby.

Fins 34 may be used in conjunction with members 52, if desired, tofurther aid in transferring heat from the members 52 to the air in theplenum 12. The hot water outlet line 36 may be connected to the waterstorage tank 16 at any convenient location in this embodiment, andpreferably near the top, as shown. The

burner 18 may be a single stage or double stage variety, f

as in the first embodiment, and is positioned conveniently beneath thetank 16.

Installation of the hydro-furnace taught by this invention is relativelyeasy since it is a self-contained unit. A separate furnace and waterheater are no longer required when the hydro-furnace is used, therefore,a substantial space savings is achieved, particularly in mobile homeswhere space is very limited.

There has thus been shown and described a single unit heating appliancefor heating potable water directly and air indirectly and maintainingcontinuous independent control over both. Although specific embodimentsof the invention have been described in detail, other variations of theembodiments shown may be made within the spirit, scope and contemplationof the invention.

Accordingly, it is intended that the foregoing disclosure and drawingsshall be considered only as illustrations of the principles of thisinvention and are not to be construed in a limiting sense.

What is claimed is:

1. A hydro-furnace for heating potable water directly and air indirectlyand maintaining continuous independent control over both, comprising:

a housing having a return register, a supply register,

and a plenum therebetween;

a water heating container disposed within said housing having a waterstorage tank, a cold water inlet, a hot water outlet, a flue extendingthrough: said housing, and a burner disposed beneathsaid'tank, forheating said potable water;

blower means disposed in said plenum for drawing:

ambient air through said return register and'blowing said air throughsaid plenum and toward said supply register;

control means associated with said blower and said burner for switchingsaid blower and said burner on and off, said control means comprising afirst thermostat responsive to room temperatures and coupled to saidblower, and a second thermostat responsive to the temperatures in saidtank and coupled to said burner, said thermostats functioningelectrically independently of one another; and

pipes coupled to the upper end of said tank at one end and to a manifoldpipe at the other, said manifold pipe being coupled to a return pipewhich is coupled to the lower end of said tank, said hot watercirculating therethrough.

3. The hydro-fumace claimed in claim 2 wherein said burner is furtherdisposed away from said return pipe.

4. The hydro-fumace claimed in claim 1 wherein said heat exchangingmeans includes multiple lateral heatconducting rods attached to theupper end of, and ex tending into said tank.

1. A hydro-furnace for heating potable water directly and air indirectlyand maintaining continuous independent control over both, comprising: ahousing having a return register, a supply register, and a plenumtherebetween; a water heating container disposed within said housinghaving a water storage tank, a cold water inlet, a hot water outlet, aflue extending through said housing, and a burner disposed beneath saidtank for heating said potable water; blower means disposed in saidplenum for drawing ambient air through said return register and blowingsaid air through said plenum and toward said supply register; controlmeans associated with said blower and said burner for switching saidblower and said burner on and off, said control means comprising a firstthermostat responsive to room temperatures and coupled to said blower,and a second thermostat responsive to the temperatures in said tank andcoupled to said burner, said thermostats functioning electricallyindependently of one another; and heat exchanging means associated withsaid water storage tank and extending into said plenum for transferringheat from said hot water to said air in said plenum.
 2. Thehydro-furnace claimed in claim 1 wherein: said burner includes a firststage coupled to said first thermostat, said first stage and said blowermeans being switched on and off essentially simultaneously by said firstthermostat, and a second stage coupled to said second thermostat, saidfirst and second stages functioning independently of one another; andsaid heat exchanging means includes multiple lateral pipes coupled tothe upper end of said tank at one end and to a manifold pipe at theother, said manifold pipe being coupled to a return pipe which iscoupled to the lower end of said tank, said hot water circulatingtherethrough.
 3. The hydro-furnace claimed in claim 2 wherein saidburner is further disposed away from said return pipe.
 4. Thehydro-furnace claimed in claim 1 wherein said heat exchanging meansincludes multiple lateral heat-conducting rods attached to the upper endof, and extending into said tank.